Combined grading and corona shield



April 10, 1956 R. 1.. M COY COMBINED GRADING AND CORONA SHIELD Filed March 29, 1955 United States Patent COMBINED GRADING AND CORONA SHIELD Robert L. McCoy, Baltimore, Md., assignor to General Electric Company, a corporation of New York Application March 29, 1955, Serial No. 497,647

9 Claims. (Cl. 174-144) .This invention relates to a combined grading and corona shield, and more particularly, to a combined grading and corona shield for strain or dead end insulators on high voltage transmission lines to provide flashover protection and improved voltage distribution on the insulator strings and to suppress corona on the articles of line hardware used to connect the transmission conductors to the insulator strings.

In the prior art many forms of combined grading and corona shields are provided which do an adequate job.

However, many of these prior art forms of combined grading and corona shields tend to be rather complicated and expensive in that they utilize a comparatively large number of separate pieces in their fabrication. Also, some of these prior art forms of combined grading and corona shields have the disadvantage of not being readily assembled or disassembled with respect to the transmission conductor, line hardware, and insulator string Without interference from said last mentioned parts. For instance, the construction of the combined grading and corona shields may be such whereby the transmission conductor can be connected to the insulator string and tensioned only by first connecting the shield with respect to the insulator string and then connecting the transmission conductor to the insulator string. This procedure results in awkward operations in properly tensioning the conductor and may result in damage to the shield or may endanger the safety to the lineman involved in the operation. Likewise, said construction may be such whereby the combined grading and corona shield cannot be removed without breaking the connection between the tensioned transmission line and insulator string.

It is an object of this invention to provide an improved and more economical combined grading and corona shield which will overcome the above discussed disadvantages of the heretofore mentioned prior art forms of combined grading and corona shields.

-My invention comprises a combined grading and corona shield having a tube or rod of metal bent into a rectangle with rounded corners having one side thereof open, a pair of tubes or rods of metal each bent into a U-shape with rounded corners, the ends of said pair of'tubes or rods connected to said one side and an opposite side of said rectangle, said pair of tubes or rods disposed in gen erally parallel planes extending generally parallel to the two other sides of said rectangle and generally perpendicular from a same side of the plane of said rectangle, and a strip of metal bent into a U-shape having the legs thereof connected to said pair of tubes or rods adjacent In the drawing, Fig. 1 is an elevation view of a preferred form of my invention. Fig. 2 is an enlarged perspective view of my preferred form of my invention. Like reference numerals will be used throughout Figs. 1 and 2 to indicate identical parts.

Referring now to the drawing, and more particularly to Fig. 1, my preferred form of invention is illustrated with respect to a transmisison line or conductor 1 dead ended to a tower structure 2 by an electrical insulator string 3. As best shown in Fig. 2, the insulator string 3 has two parallel strings of electrical insulators. Each string of the double string 3 comprises inter-connected ball and socket or eye bolt and clevis type electrical insulators which are well known in the art. The transmission line or conductor 1 is connected to the left-hand end of the double insulator string 3 by line hardware comprising a strain clamp 4, a connector 5, a flat yoke plate 6, and a pair of clevis members 7. A jumper loop 8 is electrically connected to the strain clamp 4 and extends downwardly therefrom, and the right-hand end of the double insulator string 3 is connected to the tower structure 2 in a manner well known in the art. In my invention I provide a combined grading and corona shield 9 which can be assembled with respect to the parts 1 and 3--8 without interference therefrom. That is, all the parts shown in Fig. 1 can be inter-connected and tensioned as illustrated, and then the corona shield 9 can be mounted with respect to said parts without any obstruction from said parts. Similarly, the corona shield 9 can be removed with respect to said assembled parts without breaking the tensioned connection therebetween. My combined grading and corona shield 9 will now be described with respect to Fig. 2.

The shield 9 comprises a continuous tubular or rod-like member of metal 10 having a circular cross section or rounded surfaces. Member 10 is bent into a generally flat and rectangular configuration having curved or rounded corners. The opposite ends 11 of member 10 are hemispherical or rounded, and are spaced with respect to each other whereby one side of the rectangular configuration of member 10 is open. Rectangular member 10 is concentrically disposed with respect to the line or axis of the aligned transmission line 1, line hardware 4-7, and double insulator string 3. Member 10 is disposed in generally spaced embracing relationship with respect to the outer or energized ends of the insulators of the double insulator string 3, and is generally disposed in a plane positioned substantially perpendicular to the aforementioned line or axis of the transmission line 1, line hardware 4-7, and double insulator string 3. As will be obvious to those skilled in the art, the purpose of rectangular configured continuous member 10 is to provide flashover protection and improved voltage distribution on the double insulator string 3.

The shield 9 also comprises a pair of identical continuous tubular or rod-like members of metal 12 having a circular cross section or rounded surfaces. Each of the members 12 is bent into a generally U-shape having rounded or curved corners and is connected at its opposite ends to the lower or open side of the rectangular configuration 10 and to the upper or opposite side of the rectangular configuration. As will be obvious to those skilled in the art, in order to minimize sharp projections on the shield 9 the opposite ends of the pair of U-shaped members 12 are preferably connected to the vertically disposed rectangular configured member 10 by smooth welds or the like.

The members 12 are generally disposed within generally parallel planes which extend generally parallel to the two other or left and right-hand sides of member 10 when viewing Fig. 2. Also, the members 12 extend from a same side of the flat plane of member 10 and gen- '3: an orally perpendicular thereto. That is,: themembers 12 are symmetrically positioned with respect to the axis of the transmission line 1, line hardware 47, rectangularconfiguration 10, and double insulator string 3;" and extend from the rectangular member 19 leftwardly-alongopposite sides-of line hardware -4-7 in spaced-relationshipwhen viewing Fig. 2. As will be obviousto those skilled in the art, it is a function of thepairofmemgbers-12 to suppress corona on the line hardware -4+-7.

The members it and 12 maybe-hollow tubular pieces orsolidrod-like pieces. However, in order to conserve material, in my invention members and "12* preferably are hollow tubular pieces.

The shield 9-is-provided with an attachment fitting for connecting-the shield 9 to the-flat yoke plate 6*cornprising-a continuous relatively narrow flat strip' of metal 13' bent into agenerally U-shapedconfiguration. The

legs ofthe -U-bent-strip 13 are connected to the pair of members 12by smooth welds or the like adjacent to the upperside of the rectangularly bent member 10'," and the fiat base of {the U-bent strip 13 inakesfiat surface contact with the-uppersurf ace of the flat yoke plate 6;' Strip 13:is' disposed in a plane extending generally parallel to the plane of member 16) whereby the base of strip 13is disposed adjacent the center ofr ectangular member 1013 A pair of threaded-members such-as bolts 14 extend through a not shownpair off-apertures formed-in the base of strip 13 in a direction opposite to that-of the legs of strip 13; Preferably, the bolts 14'are permanently connected to the base of-strip- 13 by welds or the like whereby the number ofloose or falling parts of theshield 9'are kept to a minimum. The notshown threaded portions of the bolts 14 extend through a not' shown pair of aligned apertures formed in the-fiat yoke plateio, and the shield 9 canbe removably and securely fastened with respect to the yoke plate 6 by-a not shown pairof self-locking nuts-threaded on the lower ends of the :bolts -14up against the underside of the flat yoke plate-6;

It is=to be noted that the-open side of the rectangular member 10: is disposedon thesarneor bottom side of thealigned" parts-1, ite 7 and 3 as jumper loop 8; When: this is done, jumper loop 3 being at the same potential as member '10, the two parts are mutually shield ing; and the presence of member 8 in the proper relationshipto the hemispherical ends 11 of member 10' posite=fr0m that illustrated in Fig-2 this would have the etfect of closing the open side of the-member10.

It willnowbe seen that my invention provides a combined; grading and corona shield for mounting with respect to a transmission conductor, line hardware, and electrical insulator string without interference or obstructiorrv therefrom. For instance, after the transmissionyline l, linehardware. 47, and double insulator string; 3yhaye.been inter-connected and tensioned theshield 9: can bereadily mounted with respect thereto by virtueof thetopen lower side of the rectangularly bent member-10. Final fastening of the'corona shield 9-re-- quires only .two looseparts such as self-locking nuts fortheaboltrmernbers 14. Similarly, the corona shield 9- can be readily removed without breaking the connection between the parts land ?;-8 merely by 'removin g the-pair of self-locking nuts and'thenliftingthe shi'el 9 away-from the-transmission line, line hardware, and insulator string assembly by virtue of the open lower sideof rectangular member 1%}.

If the I rounded base, said pair of tubular members straddling Additionally, my invention provides a combined grad ing and corona shield which; has a very small number of separate pieces whereby the corona shield is very uncomplicated and economical to manufacture. For one instance, the corona shield comprises only three separate welded pieces 10 and 12. The attachment fitting of the corona shield comprises only three separate welded pieces 13' and 14. The number of loose or fallingparts is restricted to two such as the self-locking nuts or the like for the bolts 14.

While there has been shown and described'a particular embodiment of .the invention, it will be; obvious to those skilled in the art thatchanges and modifications may be made without departing from the invention, and therefore it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim is new and desire to secure by Letters Patent of the United States is:

1'. A combined grading and corona shield comprising a tubular member having hemispherical closed ends, said" tubular member having a generally rectangular configuration open at one of the sides thereof whereby said closed ends are spaced from each other, said rectangular configuration having rounded corners, a pair of tubular members having a generally U-shaped configuration, said U- shaped'configuration having a pair of legs joined by a said-one side and the side of said 'rectangular configuration opposite to said one side and having the opposite endsthereof connected to said one and opposite sides by-smooth Welds, the planes of said pair of tubular members extending generally parallel to each other and gen erally perpendicularly from a same side of the plane of saidrectangular configuration, said pairof tubular memberplanes symmetrically disposed with respect to the centralaxis of said rectangular configuration and generally parallel withrespcct to the other two sides of said rectangular configuration, and a single piece U-shaped' attachment fitting having two leg portions connected by a generally flat base-portion, the endsof said leg portions *connected to said pair of tubular members adjacentsaid opposite side by smooth welds, the plane of said attachment fitting extending generally parallel to said rectangular configuration plane and said-base portion disposed adjacent said axis, and a pair of threaded memberspermanently connected to said base portion and-extending therefrom in a direction opposite to said leg portions.

2. A combined grading and corona-shield comprising a circular cross :sectioned continuous rod-like member havingrounded ends, said rod-like member 'b'entintoga generally rectangular configuration having curved corners;

said rounded ends spaced from each other whereby-one+ side -of said-rectangular -configuration-is;open, a pair of one side, the planes of said pair of'members extendinggenerally parallel to the other sides of said rectangular configuration 3 and-generally perpendicular from a-same side-of the plane of said rectangular configuration, and a singlepiece generally U-shaped attachment fitting having' the legsthereof connectedto the legs of said-pair of-"members adjacent'said opposite side andthe base thereof disposed adjacent the center of 'saidrectangular configuration,- the plane of said attachment fitting extending generally parallel to the plane of said rectangular configuration.

3." A combined grading and corona shield comprising a continuous rod-like member having-rounded ends bent into a rectangular configuration having rounded'corners,

said rounded ends spaced fromeach otherwhereby one= side of said rectangular configuration is open, a pair of continuous rod-like members each bent into a curved U-shaped configuration, the c ids of said pair of members connected to said one side and a side of said rectangular configuration opposite thereto, said pair of members extending from a same side of the plane of said rectangular configuration and disposed in parallel planes extending perpendicular to said rectangular configuration plane and parallel to the other sides of said rectangular configuration, and a U-shaped attachment fitting having the legs thereof connected to said pair of members adjacent said opposite side and having the base thereof disposed adjacent the center of said rectangular configuration.

4. A four piece combined grading and corona shield comprising an elongated and rounded continuous metallic member bent into a rectangle having rounded corners, opposite ends of said member spaced from each other whereby one side of said rectangle is open, a pair of elongated and rounded continuous metallic members each bent into a U-shape having rounded corners, the ends of said pair of members connected to said one side and an opposite side of said rectangle, said pair of members positioned in parallel planes disposed parallel to the other two sides of said rectangle and extending perpendicularly from a same side of the plane of said rectangle, and a continuous strip of metal bent into a U-shape having the legs thereof connected to said pair of members adjacent said opposite side and the base thereof disposed adjacent the center of said rectangle.

5. A unitary combined grading'and corona shield having only six different parts comprising an elongated and rounded continuous metallic member bent into a rectangle having rounded corners, opposite ends of said member spaced from each other whereby one side of said rectangle is open, a pair of elongated and rounded continuous metallic members each bent into a U-shape having rounded corners, the ends of said pair of members connected to said one side and an opposite side of said rectangle, said pair of members positioned in parallel planes disposed parallel to the other two sides of said rectangle and extending perpendicularly from a same side of the plane of said rectangle, and neontinuous strip of metal bent into a U-shape having the legs thereof connected to said pair of members adjacent said opposite side and having the base thereof disposed adjacent the center of said rectangle, the plane of said another strip disposed parallel to theplane of said rectangle, and a pair of threaded members connected to said base and extending in a direction opposite to said legs.

6. A combined grading and corona shield comprising an elongated metallic member bent into a rectangle having one side thereof open, a pair of elongated metallic members each bent into a U-shape, the ends of said pair of members connected to said one side and an opposite side of said rectangle, said pair of members disposed in generally parallel planes extending generally parallel to the two other sides of said rectangle and generally perpendicular from a same side of the plane of said rectangle, another elongated metallic member bent into a U-shape having the legs thereof connected to said pair of members adjacent said opposite side and having the base thereof disposed adjacent the center of said rectangle.

7. A combined grading and corona shield comprising a rounded tubular elongated metallic member bent into a rectangle having one side thereof open, a pair of rounded tubular elongated metallic members each bent into a U-shape, the ends of said pair of members con- 'nected to said one side and an opposite side of said rectangle, said pair of members disposed in generally parallel planes extending generally parallel to the two other sides of said rectangle and generally perpendicular from a same side of the plane of said rectangle, and a strip of metal bent into a U-shape having the legs thereof connected to said pair of members adjacent said opposite side and having the base thereof disposed adjacent the center of said rectangle, said strip disposed in a plane generally parallel to said rectangle plane, and a pair of attachment members connected to said base and extending therefrom in a direction opposite to said legs.

8. In a generally horizontally disposed electrical transmission conductor connected at one end thereof by metallic connecting means to one end of a generally horizontally disposed electrical insulator string, means for grading the voltage distribution along said insulator string and suppressing corona at said connecting means comprising a rounded elongated metallic member bent into a rectangle open at one side thereof, said rectangle generally surrounding said insulator string one end and generally disposed in a vertical plane, a pair of rounded elongated metallic members each bent into a U-shape and connected at the ends thereof to said one side and an opposite side of said rectangle, said pair of members positioned in generally parallel planes disposed generally parallel to the other two sides of said rectangle and extending generally perpendicularly from a same side of the plane of said rectangle along opposite sides of said connecting means, an elongated strip of metal bent into a U-shape having the legs thereof connected to said pair of members adjacent said opposite side and having the base thereof disposed adjacent the center of said rectangle, and means removably attaching said base tosaid connecting means. 7

9. In an elongated electrical conductor connected at one end thereof by a metallic yoke plate to one end of a double electrical insulator string, said conductor and string disposed along an identical generally horizontal line and a jumper loop'depending from a bottom side of said conductor, a combined voltage grading and corona suppressing shield comprising a continuous rounded tubular member bent into a flat rectangle, the opposite ends of said tubular member being rounded and spaced from each other whereby one side of said rectangle is open, a pair of continuous rounded tubular members each bent into a flat U-shape and having the opposite ends thereof connected to said one side and an opposite side of said rectangle, said rectangle and U-shape having rounded corners, said rectangle concentrically disposed about said string one end and said pair of tubular members positioned in parallel planes disposed parallel to the other two sides of said rectangle and extending perpendicularly from a same side of the plane of said rectangle along opposite sides of said yoke plate and line, said one side disposed adjacent said conductor bottom side, and a flat continuous strip of metal bent into a U-shape having the legs thereof connected to said pair of members adjacent said opposite side and having the base thereof disposed adjacent the center of said rectangle, said base making fiat surface engagement with said yoke plate and means removably attaching said base to said yoke plate.

References Cited in the file of this patent UNITED STATES PATENTS 2,306,359 Sheadel et al Dec. 22, 1942 2,539,641 Sheadel Jan. 30, 1951 2,597,590 McCoy May 20, 1952 

